As is known and understood, advances in technical knowledge often bring about re-designs of existing equipment to result in improved operation, simplicity in construction, and/or reductions in cost--amongst other advantages. In 12 channel pulse code modulation, time division multiplex communications systems, for example, such technical advances have led to development of equipment which operates at a 512 kb/s transmission rate, as compared with previous designs operating at 576 kb/s rate. Typical of such multichannel digital communictions equipments are the Army Tactical Communications Systems full duplexing transmitting equipment designated as the TD-660 (576 kg/s group rate) and the Air Force designed AN/TRC-170 tropo scatter radio terminal (512 kb/s group rate). Rather than discard all existing TD-660 units and supplanting them with replacements which operate at the 512 kb/s rate, it would be far more desirable to continue to utilize them, and as they already presently exist, but in the newly developing 512 kb/s group transmission context. One problem in doing so, however, is the incompatability which exists because of the differing group traffic rates.